This application is a National Phase Application (35 USC 371) of PCT/JP00/04622 filed Jul. 11, 2000 and claims priority of Japanese Application No. 11-202682 filed Jul. 16, 1999 and Japanese Application No. 2000-156645 filed May 26, 2000.
The present invention relates to a nanometric mechanical oscillator, a method of fabricating the same, and a measurement apparatus using the same.
Conventionally, the following techniques have been known in the field of interest.
(1) G. Binnig, C. Gerber, and C. F. Quate: Phys. Rev. Lett. 56 (1986) 930.
(2) T. D. Stowe, K. Yasumura, T. W. Kenny, D. Botkin, K. Wago, and D. Rugar: Appl. Phys. Lett. 71 (1997) 288.
(3) D. A. Walters, J. P. Cleveland, N. H. Thomson, P. K. Hansma, M. A. Wendman, G. Gurley, and V. Elings: Rev. Sci. Instrum. 67 (1996) 3583.
(4) Vu. Thien Binh, N. Garcia, and A. L. Levanuyk: Surf. Sci. Lett. 301 (1994) L224.
The scanning force microscope was invented by Gerd Binnig, et al. around 1986 (above-mentioned literature 1). Subsequently, in the mid to late 1980s, T. Albrecht, Calvin Quate, et al. developed a strip-shaped cantilever having a length of a few hundreds of microns and having at its tip a probe having a height of about 3 xcexcm. The cantilever was fabricated from silicon or silicon nitride. Since the mid to late 1980s, cantilevers of the above-described configuration have been sold in the market.
In order to measure weak force, Dan Rugar, et al. attempted to use a very thin and long cantilever (above-mentioned literature 2). Further, in order to increase the characteristic frequency of a cantilever and shorten observation time, Paul Hansma, et al. proposed a cantilever having a length of 1 xcexcm to 10 xcexcm, which is shorter than conventional cantilevers having a length on the order of 100 xcexcm (above-mentioned literature 3). Notably, the latter two cantilevers are both strip-shaped and are improved versions of the cantilever developed in the 1980s.
Meanwhile, in relation to nanometric mechanical oscillators, Vu. Thien Binh, N. Garcia, et al. demonstrated that a kokeshi-doll-shape oscillator could be fabricated through a process of heating a sharp metal probe in vacuum (above-mentioned literature 4).
Measurement of variations in the amplitude of vibration and characteristic frequency of a mechanical oscillator enables detection of variation in the mass of the oscillator and variation of a field in which the oscillator is placed.
The force detection resolution obtained by use of a mechanical oscillator increases when its characteristic frequency or quality factor increases and when its spring constant or temperature is lowered. When a mechanical oscillator can be modeled as a spring/mass system, reducing the size of the oscillator advantageously increases sensitivity.
This is because, through reduction in the mass of the mechanical oscillator, the characteristic frequency can be increased while the spring constant is maintained unchanged.
In view of the foregoing, an object of the present invention is to provide a stable and highly sensitive nanometric mechanical oscillator having a considerably high detection resolution that enables detection of variation in force or mass on the nanometer order, as well as a method of fabricating the same, and a measurement apparatus using the same.
In order to achieve the above object, the present invention provides the following.
[1] A nanometric mechanical oscillator comprising a base; a rectangular oscillator mass; and an elastic neck portion for connecting the base and the rectangular oscillator mass, the neck portion having a rectangular cross section when cut along a plane perpendicularly intersecting a main axis thereof.
[2] A method of fabricating a nanometric mechanical oscillator, comprising preparing a substrate composed of a silicon substrate, a first silicon oxide film, a silicon film, and a second silicon oxide film; forming a metal film on the second silicon oxide film; forming a rectangular mask on the metal film; etching the metal film by use of a solution and the mask; and etching vertically and successively the second silicon oxide film, the silicon film, the first silicon oxide film, and the silicon substrate through reactive ion etching, whereby a neck portion having a rectangular cross section when cut along a plane perpendicularly intersecting a main axis thereof is formed through the etching of the first silicon oxide film.
[3] A measurement apparatus comprising a nanometric mechanical oscillator including a base, an oscillator mass, and an elastic neck portion for connecting the base and the oscillator mass; a thin-film-shaped sample formed on the oscillator mass; and a stationary probe for observing the thin-film-shaped sample.
[4] A nanometric mechanical oscillator comprising a base; a tetrahedral oscillator mass; and an elastic neck portion for connecting the base and the tetrahedral oscillator mass.
[5] A method of fabricating a nanometric mechanical oscillator, comprising preparing a substrate composed of a silicon substrate, a silicon oxide film, and a silicon film; forming a tetrahedral oscillator mass on the silicon oxide film through anisotropic etching of the silicon film; etching vertically the silicon oxide film through reactive ion etching, while using the tetrahedral oscillator mass as a mask, whereby a neck portion having elasticity is formed through the etching of the silicon oxide film.
[6] A measurement apparatus comprising a nanometric mechanical oscillator including a base, a tetrahedral oscillator mass, and an elastic neck portion for connecting the base and the tetrahedral oscillator mass, wherein the tetrahedral oscillator mass is oscillated vertically relative to a surface of a sample so as to observe the surface state of the sample.
[7] A measurement apparatus comprising a nanometric mechanical oscillator including a base, a tetrahedral oscillator mass, and an elastic neck portion for connecting the base and the tetrahedral oscillator mass, wherein the tetrahedral oscillator mass is oscillated horizontally relative to a surface of a sample so as to observe the surface state of the sample.
[8] A measurement apparatus comprising a nanometric mechanical oscillator including a base, a tetrahedral oscillator mass, and an elastic neck portion for connecting the base and the tetrahedral oscillator mass, wherein the tetrahedral oscillator mass is disposed vertically in the vicinity of a surface of a right-angle prism; the surface totally reflects a laser beam entering the prism to thereby generate a photo nearfield in the vicinity of the surface; the nearfield is disturbed by oscillation of the oscillator; and generated propagating light is collected by a light receiving element in order to detect the amplitude and frequency of the oscillation of the oscillator.
[9] A measurement apparatus comprising a nanometric mechanical oscillator including a base, an oscillator mass, and an elastic neck portion for connecting the base and the oscillator mass, wherein a probe formed of a nano tube or whisker is fixed to the oscillator mass; and interaction between the probe and the sample is detected to thereby obtain an image.
[10] A measurement apparatus comprising a nanometric mechanical oscillator including a plurality of oscillator masses disposed on a base, and elastic neck portions for connecting the base and the respective oscillator masses, wherein a functional thin film is attached to each of the oscillator masses so as to detect a trace substance within a gas sample.
[11] A measurement apparatus comprising a nanometric mechanical oscillator having, on its base, an oscillator mass and an elastic neck portion for connecting the base and the oscillator mass, wherein a core of an optical fiber is fixed to the nanometric mechanical oscillator such that the oscillator faces a sample; and oscillation of the oscillator mass caused by the sample is detected optically.
[12] A measurement apparatus comprising a nanometric mechanical oscillator having, on its base, an oscillator mass and an elastic neck portion for connecting the base and the oscillator mass, wherein under vacuum, an electron beam from an electrode is radiated onto the oscillator, while being focused to have a focal point on the nanometer order; the base of the oscillator has electrical conductivity, and a portion of the oscillator exhibits a piezo effect; the oscillator causes self-excited oscillation due to current that flows upon irradiation with the electron beam and displacement of the oscillator caused by the current; and variation in current flowing out of the oscillator is detected by a high-frequency current detector to thereby detect the amplitude and frequency of the oscillation of the oscillator.
[13] A measurement apparatus comprising a nanometric mechanical oscillator having, on its base, an oscillator mass and an elastic neck portion for connecting the base and the oscillator mass, wherein through use of a solid immersion lens, a spot of light focused to a degree beyond a bendable limit is formed in the vicinity of the base of the nanometric mechanical oscillator; and the amplitude and frequency of oscillation of the oscillator are detected on the basis of return light.
[14] A measurement apparatus comprising a nanometric mechanical oscillator having, on its base, an oscillator mass and an elastic neck portion for connecting the base and the oscillator mass, wherein the oscillator is fixedly disposed on a layered substrate having a mask layer of Sb; a laser beam is radiated onto the mask layer so as to change a portion of the mask to thereby establish a state equal to formation of a nanometric opening; and thus oscillation of the oscillator only is detected.
[15] A measurement apparatus comprising a nanometric mechanical oscillator including a piezo substrate, an oscillator mass, and an elastic neck portion for connecting the substrate and the tetrahedral oscillator mass, wherein comb-shaped electrodes are disposed on the piezo substrate; and AC voltage is applied to the electrodes to thereby generate surface acoustic waves, which excite the oscillator to oscillate.
[16] A measurement apparatus comprising a nanometric mechanical oscillator having, on its base, a plurality of oscillator masses and elastic neck portions for connecting the base and the respective oscillator masses, wherein displacement of the oscillator masses which is caused upon collision of a particle with the oscillator in accordance with the law of conservation of momentum is measured so as to detect a velocity of the particle.
[17] A measurement apparatus comprising a nanometric mechanical oscillator including a base, an oscillator mass, and an elastic neck portion formed of a silicon whisker and for connecting the base and the oscillator mass, wherein the measurement apparatus measures acceleration or force.
[18] A method of fabricating a nanometric mechanical oscillator, comprising successively forming a silicon oxide film and a silicon film on a silicon substrate; anisotropically etching the silicon film to form a silicon tetrahedron; etching the silicon oxide film in a direction normal to the substrate while using the silicon tetrahedron as a mask to thereby form a silicon oxide column; vapor-depositing silicon or metal obliquely relative to the silicon substrate to thereby form a deposition film; and removing the silicon oxide column to thereby form an elastic neck portion for supporting a tetrahedral probe, the neck portion being the deposition film assuming a plate-like shape and made of silicon or metal.
[19] A method of fabricating a nanometric mechanical oscillator as described in [18], wherein the neck portion is composed of two deposition films each assuming a plate-like shape and made of silicon or metal.
[20] A nanometric mechanical oscillator including an element which comprises a first layer formed of a piezo substrate and having a surface-acoustic-wave generation unit; and a second layer having a large number of arrayed cantilevers each projecting from a base portion and having a probe, wherein the first and second layers are superposed on each other; and surface acoustic waves are generated within the piezo substrate along two directions in a plane, such that the respective probes sequentially approach a measurable region of a sample.
[21] A measurement apparatus comprising a large number of nanometric cantilevers arranged in a matrix on a substrate having an oscillating unit; a sample table on which a sample is placed to face the cantilevers; a lens system disposed on the back side of the cantilevers; an optical system for radiating light onto the lens system via a half mirror; an image capturing unit disposed at the back of the half mirror; and a display unit connected to the image capturing unit, whereby an image of the sample is displayed through action of the cantilevers.
[22] A nanometric mechanical oscillator, wherein surface-acoustic-wave generation units are disposed along four sides of a piezo substrate; and a large number of cantilevers are arranged in a matrix at a center portion thereof.
[23] A nanometric mechanical oscillator comprising: a nanometric cantilever disposed on a substrate having an actuator; and means for changing the length of the cantilever.
[24] A nanometric mechanical oscillator as described in [23], wherein the actuator is a surface-acoustic-wave generation unit.
[25] A nanometric mechanical oscillator comprising a cantilever which projects from a base, is mainly formed of a plastic containing magnetic powder, and is magnetized in a direction intersecting an axial direction of the cantilever.
[26] A nanometric mechanical oscillator comprising a cantilever which projects from a base and is mainly formed of a plastic containing whisker crystals arranged along an axial direction of the cantilever.
[27] A nanometric mechanical oscillator comprising: a cantilever which projects from a base; and a surface-acoustic-wave generation unit provided on the base in the vicinity of a root portion of the cantilever.
[28] A nanometric mechanical oscillator comprising: a cantilever which projects from a base; a surface-acoustic-wave generation unit provided on the base in the vicinity of a root portion of the cantilever; and means for changing the length of the cantilever.
[29] A nanometric mechanical oscillator comprising a triangular-pyramidal probe formed on an insulating film on a semiconductor substrate such that the probe projects outward in an overhung state.
[30] A nanometric mechanical oscillator as described in [29], wherein a single or a large number of triangular-pyramidal probes are formed at the tip of a semiconductor chip.
[31] A nanometric mechanical oscillator as described in [27], wherein the cantilever has a triangular-pyramidal probe that projects outward.
[32] A nanometric mechanical oscillator as described in [27], wherein a large number of triangular-pyramidal probes are formed at the tip of a semiconductor chip.
[33] A nanometric mechanical oscillator comprising a parallel-spring supported portion including two triangular-pyramidal probes which are formed on a semiconductor substrate such that the probes project inward in an overhung state and are connected to each other.
[34] A nanometric mechanical oscillator comprising a parallel-spring supported portion including a probe assuming the form of a triangular prism projecting from a semiconductor substrate.
[35] A nanometric mechanical oscillator comprising a parallel-spring supported portion including a mass formed on a semiconductor substrate and assuming the shape of a truncated rectangular pyramid.